The present invention relates to a crusher and more particularly to a crusher of the type in which the raw material is crushed by forcing it to collide with striking members or hammers revolving at a high speed within a crusher frame.
In general, there have been known two types of crushers in which a raw material is crushed by causing it to be impinged upon striking members such as striking plates, hammers, etc. revolving at a high velocity within the crusher frame, i.e. one in which the rotary shaft carrying the striking members is disposed horizontally, and another in which the rotary shaft is vertical. In both types, it is a well known fact that as the particle diameter of the raw material to be crushed becomes small the crushing of such material is made difficult. In order to carry out the crushing effectively it has been a common practice to increase the rate of rotation of the rotary shaft for the purpose of realizing a greater impact generated at the time of the collision of the raw material with the striking members. However, as the particle diameter of the raw material becomes small, the mass of the material also becomes small so that not only does the impact given thereto at the time of the collision with the striking members become small, but also, since the air surrounding the material is severely agitated by the stiking members as well as the parts supporting them which are revolving at a high velocity, the raw material having a small particle diameter can be easily accelerated by the agitated air, resulting in a decrease in the difference in velocity between the material and the striking members, thus reducing the crushing force caused by the collision. In extreme cases, it may happen that the raw material escapes sideways without impinging upon the striking members. Therefore, in the case where the particle diameter of the raw material is small, it is very difficult to effectively crush it by merely increasing the rate of rotation of the striking members. Nevertheless, it is a known fact that although the known crushers of these types have the defects as above described, they have been used more than crushers of other types, e.g. rod mills, roller mills, etc. because they are simple in construction, small in size in relation to capacity, small in the amount of space required for the installation, etc.